1. Field of the Invention
The present invention relates to a work system which includes an arm mechanism used to execute a predetermined work for a target object, and an information processing method in the work system.
2. Description of the Related Art
In a work system which includes an arm mechanism used to execute a predetermined work for a target object whose position and orientation change, the position and orientation (three-dimensional (3D) information) of the target object are required to be measured upon execution of the work, and a light-section method is known as the measuring method.
The light-section method is a method that acquires 3D information of the target object by executing a triangulation by combining a camera and slit light projector, and various proposals about this method have been conventionally made in association with application to the work system.
For example, Japanese Patent Laid-Open No. 2005-271103 proposes a position calibration method of an origin when a 3D scanner (image sensing device and slit light projector) is mounted on a robot arm. Also, Japanese Patent Laid-Open No. 2005-163346 discloses a method of focusing an emitted beam light on a target object when a 3D scanner (image sensing device and slit light projector) is mounted on a robot arm.
However, both the work systems disclosed in these patent references are premised on the arrangement which integrates the image sensing device and slit light projector. For this reason, if the image sensing device is arranged at a global position (a fixed position not on the robot arm), the slit light projector is also arranged at the global position. When the image sensing device is arranged on the robot arm, the slit light projector is also fixed on the robot arm.
However, when the image sensing device and slit light projector are arranged at the global position, occlusion of slit light emitted by the slit light projector by the target object itself or the robot arm cannot be avoided depending on the position or orientation of the target object. Also, the focal depth of the emitted slit light often limit a precise measurement range. These problems disturb achievement of high measurement precision.
On the other hand, when the image sensing device and slit light projector are arranged on the robot arm, they cannot be arranged so as to be spaced apart from each other. Since the light-section method measures based on the principle of triangulation, when the distance between the image sensing device and slit light projector is short, and an angle the optical axis of the image sensing device makes with that of the slit light projector (optic angle) is small, the measurement precision in the depth direction is decreased.
When the robot arm has a small size, it is difficult to arrange the image sensing device which has a high resolution and a large weight. In this case, high measurement precision cannot be expected.